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Finite element modelling of medical devices
Medical Engineering & Physics 31 (2009) 419
Contents lists available at ScienceDirect
Medical Engineering & Physics journal homepage: www.elsevier.com/locate/medengphy
Editorial
Finite element modelling of medical devices
Society expects effective and reliable medical devices. Clinical trials are the ultimate test, but engineers need to test devices before they are ever implanted in patients [1]. Such pre-clinical tests include computational modelling, animal experimentation, and bench testing with physical models and cadavers. It is computational modelling that is undergoing the most rapid growth at the moment; increasing computational power is becoming available; imaging allows the creation of patient-specific models; and the algorithms behind mechano-regulated processes are being discovered. Indeed, combining these aspects to create ‘virtual environments’ as platforms for testing medical devices has set new goals for bioengineering of medical devices [2]. The papers in this special issue were first presented at the Summer Workshop of the European Society of Biomechanics held in Dublin in August 2007. Our aim in collecting these papers for a special issue of Medical Engineering & Physics has been to illustrate the practical application of finite element modelling to implantable medical devices across a range of medical disciplines including regenerative medicine, cardiology, and orthopaedics. Application across the medical disciplines brings up the same issues again and again: (i) Effective corroboration of finite element models with experiments, (ii) Turning finite element models into valuable design tools, (iii) Using finite element models to drive algorithms for mechanoregulated processes, (iv) Interpreting results: a particular issue of current interest is interpreting deterministic models of either ideal or patientspecific cases in the context of variability found when the device is released into the human population. These issues are addressed in the papers collected here. It is clear that the reliability of finite element models is increasing, but it is not possible to have total validation—a totally valid model would be the reality itself! As we stated in the introductory lecture to the symposium,
interest biological adaptations of the tissues must be incorporated into the simulations—simulation of mechanical failure modes alone is not usually sufficient. Finally the issue of interpreting results: given the variability in biological reactions of tissues across the human population, obtaining deterministic analyses of wide applicability is an impossible goal. The incorporation of variation due to environment (loading) and genetic differences to create stochiastic simulation is the next major objective. If this is true then finite element modelling may need to rely less on validation of one specific model than on corroboration against a range of outcomes observed in clinical studies. Getting to this stage will require improvements in computational capabilities, informed experimental work and clinical testing and, multidisciplinary collaborations that involve finite element experts but also statisticians, biologists and clinicians. The future of numerical models in medical device design therefore relies on our ability to draw these disciplines together in new and creative ways. Finally we would like to thank the authors of the papers for submitting to this special issue. We also thank the reviewers for the time they have given to the review process. The workshop grant from Science Foundation Ireland enabled us put on the symposium where the papers were first presented and we thank them for their support. References [1] Prendergast PJ, Maher SA. Issues in pre-clinical testing of implants. Journal of Materials Processing Technology 2001;118:337–42. [2] Viceconti M, Testi D, Taddei F, Martelli S, Clapworthy GJ, Van Sint Jan S. Biomechanics modelling of the musculoskeletal apparatus: status and key issues. Proceedings of the IEEE 2006;94:725–39. [3] Prendergast PJ, Lennon AB. An introduction to the workshop on finite element modelling in biomechanics and mechanobiology. Finite element modelling biomechanics and mechanobiology. Dublin: Trinity Centre for Bioengineering; 2007, p. 1–4 (available at www.tcd.ie/bioengineering/documents/ Chapter1 ESBWorkshop.pdf; last accessed March 6, 2009).
Patrick J. Prendergast a,∗ Caitríona Lally b Alexander B. Lennon a a Trinity College Dublin, Ireland b Dublin City University, Ireland
“The process of validation is never fully complete. Validation continues until the researcher becomes satisfied that the model can answer the research question posed. Needless to say, some researchers are more easily satisfied than others . . ..” [3]. If the model has been corroborated for use in some problems, it is natural to use it as a design tool. But an issue not to be forgotten is that a design tool can only monitor for failure modes included in the model; since long-term failure modes are now the ones of most
1350-4533/$ – see front matter © 2009 Published by Elsevier Ltd on behalf of IPEM. doi:10.1016/j.medengphy.2009.03.002
∗ Corresponding
author at: Trinity Centre for Bioengineering, School of Engineering, Trinity College, Dublin, Ireland. Tel.: +353 1 896 3393; fax: +353 679 5554. E-mail address: [email protected] (P.J. Prendergast)
Contents lists available at ScienceDirect
Medical Engineering & Physics journal homepage: www.elsevier.com/locate/medengphy
Editorial
Finite element modelling of medical devices
Society expects effective and reliable medical devices. Clinical trials are the ultimate test, but engineers need to test devices before they are ever implanted in patients [1]. Such pre-clinical tests include computational modelling, animal experimentation, and bench testing with physical models and cadavers. It is computational modelling that is undergoing the most rapid growth at the moment; increasing computational power is becoming available; imaging allows the creation of patient-specific models; and the algorithms behind mechano-regulated processes are being discovered. Indeed, combining these aspects to create ‘virtual environments’ as platforms for testing medical devices has set new goals for bioengineering of medical devices [2]. The papers in this special issue were first presented at the Summer Workshop of the European Society of Biomechanics held in Dublin in August 2007. Our aim in collecting these papers for a special issue of Medical Engineering & Physics has been to illustrate the practical application of finite element modelling to implantable medical devices across a range of medical disciplines including regenerative medicine, cardiology, and orthopaedics. Application across the medical disciplines brings up the same issues again and again: (i) Effective corroboration of finite element models with experiments, (ii) Turning finite element models into valuable design tools, (iii) Using finite element models to drive algorithms for mechanoregulated processes, (iv) Interpreting results: a particular issue of current interest is interpreting deterministic models of either ideal or patientspecific cases in the context of variability found when the device is released into the human population. These issues are addressed in the papers collected here. It is clear that the reliability of finite element models is increasing, but it is not possible to have total validation—a totally valid model would be the reality itself! As we stated in the introductory lecture to the symposium,
interest biological adaptations of the tissues must be incorporated into the simulations—simulation of mechanical failure modes alone is not usually sufficient. Finally the issue of interpreting results: given the variability in biological reactions of tissues across the human population, obtaining deterministic analyses of wide applicability is an impossible goal. The incorporation of variation due to environment (loading) and genetic differences to create stochiastic simulation is the next major objective. If this is true then finite element modelling may need to rely less on validation of one specific model than on corroboration against a range of outcomes observed in clinical studies. Getting to this stage will require improvements in computational capabilities, informed experimental work and clinical testing and, multidisciplinary collaborations that involve finite element experts but also statisticians, biologists and clinicians. The future of numerical models in medical device design therefore relies on our ability to draw these disciplines together in new and creative ways. Finally we would like to thank the authors of the papers for submitting to this special issue. We also thank the reviewers for the time they have given to the review process. The workshop grant from Science Foundation Ireland enabled us put on the symposium where the papers were first presented and we thank them for their support. References [1] Prendergast PJ, Maher SA. Issues in pre-clinical testing of implants. Journal of Materials Processing Technology 2001;118:337–42. [2] Viceconti M, Testi D, Taddei F, Martelli S, Clapworthy GJ, Van Sint Jan S. Biomechanics modelling of the musculoskeletal apparatus: status and key issues. Proceedings of the IEEE 2006;94:725–39. [3] Prendergast PJ, Lennon AB. An introduction to the workshop on finite element modelling in biomechanics and mechanobiology. Finite element modelling biomechanics and mechanobiology. Dublin: Trinity Centre for Bioengineering; 2007, p. 1–4 (available at www.tcd.ie/bioengineering/documents/ Chapter1 ESBWorkshop.pdf; last accessed March 6, 2009).
Patrick J. Prendergast a,∗ Caitríona Lally b Alexander B. Lennon a a Trinity College Dublin, Ireland b Dublin City University, Ireland
“The process of validation is never fully complete. Validation continues until the researcher becomes satisfied that the model can answer the research question posed. Needless to say, some researchers are more easily satisfied than others . . ..” [3]. If the model has been corroborated for use in some problems, it is natural to use it as a design tool. But an issue not to be forgotten is that a design tool can only monitor for failure modes included in the model; since long-term failure modes are now the ones of most
1350-4533/$ – see front matter © 2009 Published by Elsevier Ltd on behalf of IPEM. doi:10.1016/j.medengphy.2009.03.002
∗ Corresponding
author at: Trinity Centre for Bioengineering, School of Engineering, Trinity College, Dublin, Ireland. Tel.: +353 1 896 3393; fax: +353 679 5554. E-mail address: [email protected] (P.J. Prendergast)